(1) Field of the Invention
The present invention relates to a fixing device and an image forming apparatus, and in particular to a technique for preventing an electrode from peeling off from a resistive heater in a fixing device that fuses a toner image onto a recording sheet by Joule heat generated by applying an electric current to the resistive heater.
(2) Related Art
Conventionally, a structure that is widely used in fixing devices is to fuse a toner image onto a recording sheet by heating the toner image with use of a ceramic heater. In this structure, a fixing belt, which is endless and wound around a fixing roller, is pressed against a pressure roller and driven to rotate. When the recording sheet passes through between the fixing belt and the pressure roller, the toner image, which is heated with use of the ceramic heater, is fused onto the recording sheet.
However, there is always a demand for further shortening warm-up time required for raising a fixing belt to a fixing temperature and further reducing power consumption. To meet this demand, a structure is proposed to provide a resistive heater for a fixing belt, and to apply an electric current to the resistive heater to generate Joule heat. In this way, a toner image is fixed by the Joule heat. According to this structure, it is possible to shorten the warm-up time and save power consumption.
In a case where the aforementioned structure is employed for a fixing device, a fixing belt is rotatably wound around a fixing roller to reduce a contact area between the fixing belt and the fixing roller. This helps prevent heat from escaping from the fixing belt to the fixing roller, thus shortening the warm-up time. However, winding the fixing belt in such a manner may cause the fixing belt to meander with respect to the fixing roller. To address this problem, a meander regulation plate for regulating the meandering of the fixing belt is provided for each side of the fixing belt, such that each of the meander regulation plates makes contact with a respective edge of the fixing belt in a direction of a rotation axis thereof.
However, in order to apply an electric current to the resistive heater, the fixing belt includes electrodes which are each provided circumferentially at a respective end of the fixing belt in a direction of the rotation axis. Therefore, when the fixing belt meanders, the electrodes are subjected to a stress by sliding against the meander regulation plates, and peel off from the resistive heater. When the electrodes peel off from the resistive heater, not only is the fixing belt damaged, but smoking or firing may occur due to variations in current density in the resistive heater, discharge at the peeled portion of the electrodes, etc.